Terry's DRSSTC About finished ;-)

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Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

I ran my DRSSTC into a primary coil and cap (but just battery power):

http://drsstc.com/~terrell/pictures/PowerTest.JPG


The six 9V batteries easily pumped 10 amps at about 60kHz into the 
primary.  The unloaded primary's LC resistance is 100 ohms so 10 amps 
represents 1000V.  It could have gone much higher but I did not have 
anything insulated or set up to push any real voltages.  The over current 
works fine even way down at 10 amps.

http://drsstc.com/~terrell/pictures/OutputLCdrive.gif

Sort of an interesting picture.  The first downward pulse on the yellow 
trace (output voltage) is the startup circuit pulse.  Then the digital CT 
has enough signal to drive it onward.  For the first 80uS, it is driving 
current into the primary.  Then it is switched off By the fiber optic 
remote controller and the energy in the primary LC is sucked back up into 
the box.  Note the voltage phase shift in the middle.  That surprised me at 
first, but I guess it knows what it is doing ;-)  The first 5 voltage 
pulses are driven from the IGBTs while the trailing 4 pulses are the 
reverse diodes in the IGBTs feeding the primary LC voltage back into the 
buss rails.


The gate drive signals are fast and solid with rise and fall times at about 
100 - 150 nS (these are at the IGBT gates under power).  There is some high 
speed glitching.  Hard to tell if that is from the differential probe just 
picking up noise or if it is really there.  I will order up a load of 
ferrites from DigiKey just in case.  I did clean up some gate drive wiring 
which should help too.  The gate drive cards have no problem at all driving 
the gates.

http://drsstc.com/~terrell/pictures/GateDriveSignals.gif


So I put it all together and powered it up!!

http://drsstc.com/~terrell/pictures/FullyPowered.JPG

Nothing was connected and no drive signal but at this point the buss is 
fully loaded for bear and the IGBTs are fully charged and the logic is in 
full control.  If anything were wrong, it would have blown up here.  I put 
the cover on the contain any flying burning fragments, but all went fine ;-)

The only real change was to make the charging resistor 50 ohms and fuse 
it.  The 100mA of current needed by the gate drive cards loaded down the 
250 ohm resistor and it could only charge the buss to 240V.  The 50 ohm 
resistor charges to 305 so no problem when the bypass is thrown in 
"snapping" the buss voltage to the full 340 VDC.

I still have not put the remote control board in it's box so I still need 
to do that.  I will also look more into the gate glitches.  I think I will 
set the IGBT temperature limit at 50C and the current trip at 50 amps for 
starters.  The fan is sort of blocked right now, but if it does not need 
more flow I will just leave it as is.  It "seems" like it will be fine.  I 
think I can just run my big coil as is with it to start but probably just 
run the primary with a big resistor in series at first.

I took a bunch of pictures inside on out:

http://drsstc.com/~terrell/pictures/F-Front.JPG
http://drsstc.com/~terrell/pictures/F-Back.JPG
http://drsstc.com/~terrell/pictures/F-FrountInside.JPG
http://drsstc.com/~terrell/pictures/F-RightInside.JPG
http://drsstc.com/~terrell/pictures/F-LeftInside.JPG
http://drsstc.com/~terrell/pictures/F-BackInside.JPG
http://drsstc.com/~terrell/pictures/F-H-Bridge-Drive.JPG

Cheers,

	Terry